Thermal orientation of electron spins

Abstract

It is shown that the spin orientation of free electrons occurs in low-symmetry semiconductor structures if only the electron gas is driven out of thermal equilibrium with the crystal lattice. The proposed mechanism of such a thermal orientation of electron spins is based on spin dependence of the electron-phonon interaction which tends to restore equilibrium. The microscopic theory of the effect is developed here for asymmetric (110)-grown quantum wells where the electron gas heating leads to the spin orientation along the [110] axis in the quantum well plane.

Giant photocurrents in a Dirac fermion system at cyclotron resonance

“…In such a coordinate system, the basis functions of the 6 and 8 bands can be presented in the form The deformation interaction of electrons with acoustic phonons in zinc-blende-type crystals has both intraband and interband contributions. [54][55][56] The matrix elements of straininduced interband coupling are given by V S,X = cv u y z , V S,Y = cv u x y , V S,Z = cv u x y , where cv is the interband constant of the deformation potential and u αβ are the straintensor components used here in the primed coordinate system. Note that cv = 0 in noncentrosymmetric crystals only.…”

“…We consider that at low temperatures, relevant to the experimental conditions, the momentum relaxation of carriers is limited by elastic scattering from static defects while the energy relaxation is governed by deformation interaction with bulk acoustic phonons. The spindependent asymmetry of electron-phonon interaction in (013)-grown QWs is caused by the strain-induced coupling between the Γ 6 and Γ 8 band states [50][51][52] and deviation of the QW plane from the (001) plane by the angle θ ≈ 18.4 • . Then, for the linear electron dispersion in QWs with symmetric confinement potential, the resulting fluxes have the form (see Supplementary Material)…”

“…exp(iq z z)dz, Ξ c and Ξ v are the deformation-potential constants in the bands Γ 6 and Γ 8 , respectively, and Ξ cv is the interband deformationpotential constant [51,52].…”

Pure spin photocurrents

“…As a more detailed example, we consider the (110)-grown QWs. In this case the dominant spin-dependent contribution to the Hamiltonian of electron-phonon interaction in the deformation-potential model is proportional to σ z ′ (k x ′ + k ′ x ′ ), and the corresponding Hamiltonian has the form [39] …”